Effect of Single and Multi-directional Shakings on Soil Liquefaction

• Main Authors: Che-An Lee, 李哲安
• Other Authors: 翁作新
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/81817305061416538590

碩士 === 國立臺灣大學 === 土木工程學研究所 === 100 === In order to study the effect of one- and two-dimensional shakings on soil liquefaction, the test data obtained from shaking table tests at the National Center for Research on Earthquake Engineering were processed and analyzed. Test specimens include two kinds of sand. One is clean Vietnam silica sand and the other is Mailiao sand with fines. The Vietnam sand is white and sub-angular quartz sand from Da Nang, Vietnam. The Mailiao sand is a typical silty sand in the western coastal area of Taiwan. The test data contain nine series of Vietnam sand and two series of Mailiao sand. This study used the data from piezometers within the specimen to investigate the effect of two-dimensional shaking on pore water pressure generation in sand. Within the non-liquefied zone of Vietnam sand and Mailiao sand specimens, excess pore water pressures generated under two-dimensional shakings were always greater than those under one-dimensional shakings. It was also found that the ratios between the maximum excess pore water pressure generated under one- and two-dimensional shakings were similar at all locations of the piezometers within the specimen. This study uses the pore water pressure ratio (ru = Δu / σv '') as the parameter to compare the test results under one-dimensional shaking and two-dimensional shaking. In the case of the Vietnam sand specimen, the ratio of maximum ru under 2D shaking to that under 1D shaking is about 5.76, and the ratio of maximum ru under 2D shakings to that under 1D shaking is about 3.2 in the case of the Mailiao sand specimen. The depth of liquefaction was determined based on the measured pore water pressures in the sand specimen and accelerations on the frames of the shear box. It was found that the influences of shaking frequency and duration on the depth of liquefaction are not remarkable. The liquefaction depth increases slightly with increasing amplitude of shaking (maximum acceleration). With the same testing conditions, the liquefaction depth under two-dimensional shakings is approximately equal to that under one-dimensional shakings. Only a small number of two-dimensional shaking tests caused larger depth of liquefaction than one-dimensional shakings.